Insight to Depth of Field

[AlphaZeroOne]

This may be of absolutely no use to anyone but I have always struggled with understanding DoF. I understand all the theory but I am a 'visual' person who needs to see the picture. So yesterday I set my camera up on a tripod, focused the macro lens on an orchid flower and shot of the whole f range using the Av mode.

I then imported all the shots into PSE 5 and, using the 'flick' picture feature was able to play the whole sequence in a matter of a minute or so. I was able to slow the playback rate down and see for myself the effects of the DoF at each f stop. I was then able to 'flick' back an forwards to really see the difference that the changes to f stops make to the focused parts of the orchid.

Simple, but it worked for me!

[cannylad]

Sounds a good way of relating to DOF, did you notice a great difference and did your camera produce better results around a certain F stop.

Never thought of trying this in macro.

brian.

[Little Richardjohn]

Originally Posted by AlphaZeroOne

This may be of absolutely no use to anyone but I have always struggled with understanding DoF. I understand all the theory but I am a 'visual' person who needs to see the picture. So yesterday I set my camera up on a tripod, focused the macro lens on an orchid flower and shot of the whole f range using the Av mode.

I then imported all the shots into PSE 5 and, using the 'flick' picture feature was able to play the whole sequence in a matter of a minute or so. I was able to slow the playback rate down and see for myself the effects of the DoF at each f stop. I was then able to 'flick' back an forwards to really see the difference that the changes to f stops make to the focused parts of the orchid.

Simple, but it worked for me!

It sounds daft, but if you think of the total amount of 'focus' as a tube of toothpaste, the smaller the hole/aperture the longer the strip of toothpaste extruded. You get the same effect if you look through any hole smaller than your pupil. Looking through a pinhole, for instance, puts the world into sharper focus. Increasing depth of field is what you do when you narrow your eyelids to see into the distance.

And of course, the wider the angle of the lens, the greater the depth of field.

[AlphaZeroOne]

Originally Posted by Little Richardjohn

It sounds daft, but if you think of the total amount of 'focus' as a tube of toothpaste, the smaller the hole/aperture the longer the strip of toothpaste extruded. You get the same effect if you look through any hole smaller than your pupil. Looking through a pinhole, for instance, puts the world into sharper focus. Increasing depth of field is what you do when you narrow your eyelids to see into the distance.

And of course, the wider the angle of the lens, the greater the depth of field.

And daft about sums me up! I still can't get me head around this aperture and DoF. It's bit like when I first came across Boolean Algebra and 'logic'. How can 1 + 1 make 3! (Well it can, using a base 2.) And the logic of aperture is just as bewildering to me. So, the smaller the number the larger the aperture, the more exposure the less focus. But thanks for taking the time to explain your analogy of the tooth paste RichardJohn. Some people are just beyond help and I am at the front of that queue! LoL

[Tormentil]

B---------A--------C

Depth of field... If 'A' is the object being photographed, everything between 'B' and 'C' will be in focus (sharp); everything outside 'B' & 'C' will be out of focus (blurred).

The distance between 'B' & 'C' varies, depending on the aperture used.

A bit simplistic, but thats about it.

[Rookie 300d]

I'm going to try this but i don't have PSE 5, Does any one know if i can do this on Photoshop CS2?

[Little Richardjohn]

Originally Posted by AlphaZeroOne

And daft about sums me up! I still can't get me head around this aperture and DoF. It's bit like when I first came across Boolean Algebra and 'logic'. How can 1 + 1 make 3! (Well it can, using a base 2.) And the logic of aperture is just as bewildering to me. So, the smaller the number the larger the aperture, the more exposure the less focus. But thanks for taking the time to explain your analogy of the tooth paste RichardJohn. Some people are just beyond help and I am at the front of that queue! LoL

This looks like a case of blackboarditis.

Try the pinhole experiment. The ideal subject for this is slightly myopic.
If you are, take off your specs and look through a pinhole. Your eyesight improves. The depth of field of your lens is extended by the small aperture. The light, and with it the 'amount' of focus, is 'squeezed' into a longer cylinder entering your brain. Or in the case of the camera, falling on the film or ccd.

This is very fallible from a strictly scientific point of view, but helps visualise the concept. There are other ananlogies.
The classic shot to illustrate this is the one of fenceposts receding into the distance. Using a wide aperture, focus on the foreground, middle-distance, and the far-distance, using different focal lengths. Then repeat using a small aperture.

Incidentally. this is interesting.
"the more exposure the less focus."
You mean, the wider the aperture, the less focus. A wider aperture will require a correspondingly shorter shutter speed to provide the right exposure. So a wide aperture does not in itself provide 'more exposure', merely less depth of field.

Don't worry about the apparent reverse numbering. In time, you will see each aperture not as a number but as a specific photographic tool, each giving its own characteristics to the shot. A bit like keys in music.

[MalcolmX]

if you wish you can take a series of photgraphs on a tripod (do not move the camera)and using adobe bridge merge to hdr which will give you a shot with focus right throught the frame , this is the same technique that astonomers use to get sharp pictures of stars ,.
another way is to open up the shot into different layers and then rub out the out of focus bits then merge the layers
lot of work but it is a valid way of eliminating out of focus bits

[nightshade]

Just to help this along Hyperfocal Distance and Depth of Field Calculator - DOFMaster I can always remember being told of the Hyperfocal distance and how useful it was in landscape photography looking up an explanation I came across this apparently useful site

[Kev Lewis]

If you just stick to F numbers rather than aperture size then:

A small F number will give a small DOF ie F2.8 gives a smaller DOF than F16.

To make the most of the DOF you have it is worth knowing that 1/3 of the DOF will be in front of the focus point and 2/3s of the DOF is behind the focus point.

NOte: If you close the aperture too much then the DOF will increase BUT the overall sharpness of the image will decrease due to defraction limitations but thats another kettle of fish Most lens are sharpest when they are stopped down only 2 or 3 stops from fully open.

If you want to combine images shot at the same same aperture but with the focus point moved through the image I would recommend a programme called CombineZ5, google will find it and it's free. I uploaded a couple of images of a fok awhile back showing this programme in use